Before Richardson police Officer David Sherrard was shot and killed, I bumped into a veteran Dallas officer I hadn't seen in a few weeks. He's a big, imposing figure who looks like he should be playing defensive end in the NFL.

Not a guy you'd want to get cross with.

We talked about the everyday stresses of his jobs in a department that remains shorthanded and stretched to the max.

I made an off-the-cuff remark about how tough it must be just to deal with routine calls. His ears perked up. "Man, let me tell you," he said. "There's no such thing as a routine call. You got so many people out here with mental illness, doing that K2 and other drugs, you just don't know what you'll run into."

His words, haunting and honest, came rushing back to mind as I watched our community absorb the death of Sherrard, who was buried Tuesday. But even in this hour of sorrow and grief, time did not stand still for all of those who pin a badge on their chest, right above their hearts, each day.

In a painful, tragic twist for law enforcement officers around the country, another police officer — a commander — was shot in downtown Chicago just as services were getting underway for Officer Sherrard in Dallas. Sherrard was killed responding to a disturbance call at a Richardson apartment where another man, Rene Gamez, also was fatally shot.

That means nationwide, we've lost 16 officers this year, including one federal agent, as of Valentine's Day. Most of them — a dozen fallen roses — were gunned down responding to calls, a reminder of the volatile, treacherous work of first responders.

No two days, no two calls are ever the same.

Nothing can be taken for granted.

Sherrard was the first Texas officer killed this year — and hopefully the last. But thus far, communities in a dozen states have been left mourning.

And I've been thinking a lot about what it means to be a "hero," a term we tend to toss around too casually these days. A Willie Nelson classic comes to mind: "My Heroes Have Always Been Cowboys."

As a country boy myself, the son of a ranch hand who embodied that American frontier spirit, I always crank up the radio when that song comes on.

As much as I can relate to the lyrics, I've always been able to separate the mythical image of the West from reality. A hero is someone who has nothing to gain and a lot — possibly everything — to lose by helping someone else.

A few years ago, in a piece he penned for Psychology Today, Dr. Alex Lickerman, the former director of primary care at the University of Chicago, dissected the difference between courage and heroism.

"What actually makes a hero?" Lickerman wrote. "I'd argue it's the willingness to make a personal sacrifice for the benefit of others. If you don't find yourself having to resist a voice inside your head urging you to save yourself instead of whatever action you're contemplating, my heart, at least, will refuse to recognize your actions — however legitimately compassionate or courageous they may be — as heroic.

"Serving others," Lickerman said, "while simultaneously serving oneself can be noble, certainly, but a special kind of nobility attaches itself to those who serve others at a cost to themselves. That's the nobility that tugs at my heart. That's the kind of behavior I find heroic."

That's what Sherrard, 37, and his other fallen colleagues did: They put their lives on the line day in and day out.

"He made that sacrifice coming to the aid of people he'd never met, people he didn't even know," Richardson Police Chief Jimmy Spivey said while choking back tears. "It was no accident that David Sherrard was No. 1 in that stack that went into that apartment. David knew it was his time to lead. He knew that people depended on him. And he rose to that occasion."

Richardson police Officer David Sherrard was killed Feb. 7 in a shooting at an apartment complex.

(Richardson Police Department)

One former officer, Haley Adams, took her 5-year-old daughter to watch the funeral procession.

"It was the least I could do," she told NBC5. "This officer had kids. Definitely gets me right in the heart. Too many."

Another man, Tory Mcgee, took his 7-year-old twins out of school early so they could see the procession. "He has people who loved him," McGee said. "He didn't deserve to die like that."

The same can be said of all 16 officers — thus far — who've sacrificed their lives this year in the name of public safety. They didn't lead routine lives.